1. Field of the Invention
This invention relates generally to a Push to talk over Cellular (PoC) service, and more particularly, to a system and method that efficiently manages a connection while providing the PoC service.
2. Description of the Related Art
The 3rd Generation Partnership Project Internet Protocol (IP) Multimedia Subsystem (3GPP IMS) standard includes a standard regarding a PoC service and a Push-To-Talk (PTT) specification. The PTT, which is also known as Press-To-Transmit, is a method of conversing on half-duplex communication lines, where users set a transmission mode or a reception mode by operating a switch.
For example, users set a PTT device to a transmission mode by pressing the mode switch and revert to reception mode by releasing the mode switch. That is, a PTT device user A talks into a microphone while pressing the mode switch of the user A's PTT device, and another user B, who has subscribed to the same PTT group as user A, stands by, without pressing a mode switch of user B's PTT device. Accordingly, user B can hear what user A is saying via user B's PTT device. A typical example of a device using PTT is a handheld transceiver or a walkie-talkie.
PoC services refer to PTT services that are provided via a cellular communication network. Cellular communication networks support full-duplex via Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), etc. If the networks use PoC services, they can transmit messages to a User Equipment (UE) that is not currently connected thereto, instead of half-duplex communication, because cellular mobile phones and cellular communication networks employ PoC services.
PoC services are provided based on PoC groups. For example, if a PoC group, G1, includes PoC devices, A, B, and C, data that device A transmits to group G1 in a transmission mode can be shared by devices B and C.
Further, one PoC device may be subscribed to a number of PoC groups. In that case, the PoC device selects which of the PoC groups it wants to transmit a corresponding message to or receive a corresponding message from.
A PoC application server identifies a PoC group session or the number of connections, executed according to the request of user equipment, in an environment where services are provided, according to a conventional IMS standard, via a mobile communication network. However, if communication congestion occurs in a PoC group in a cell, the PoC application server detects the congestion and controls the group calls.